The disclosure relates generally to torque (linear motion and rotation) transmission assemblies and optical sensing devices utilizing torque transmission assemblies, and more particularly to optical coherence tomography (OCT) systems and OCT probe assembles which may be used in medical applications.
Torque transmission and sensing devices, are suitable for use in medical sensing applications, for example, in optical coherence tomography (OCT). In optical coherence tomography, this can be done inside a living body by utilizing a small optical probe component (miniature optic sensor) to image light onto an organic material (for example biological tissue), and to collect the light scattered back by the organic material. The optical probe assembly, including the optical probe component is inserted inside the body, for example through the blood vessels or gastro intestinal tracks, to obtain an image of the inside surfaces of the tissues such as blood vessels, or tissues of the intestinal track.
More specifically the optical probe component moves inside a body to obtain sub-surface 3D (three dimensional) information of tissues. Light back scattered from the tissues at different depths is monitored using the interferometric techniques and a 3D scan of tissues is obtained. The 3D scan is achieved by rotating the optical probe component at high speeds (for example 1000 rpm) in a controlled fashion. This rotation has been achieved using a stainless steel coiled wire torque spring component into which at the fiber and at least a part of the optical probe assembly is incorporated. The stainless steel coiled wire torque spring component and the rest of the optical probe assembly are then threaded through a closely fitting transparent polymer tube referred to as inner lumen. During OCT device operation, the optical probe component and the stainless steel coiled wire torque spring component rotates inside of the inner lumen, and the inner lumen protects the tissues from contact with the rotating probe.
The stainless steel coiled wire torque spring component typically includes multi-coil stainless steel spring, but can include a single wire coil (see FIGS. 1A and 1B, for example). The coiled wire can stretch, so that the spacing between coils can expand or contact under sufficient force. The spring rate k (where k is a spring constant or a force constant of the spring) for such coiled wire torque spring component is around 500N/m under stretching/pulling—i.e., coiled wire torque spring component can stretch relatively easily when pulled. An optical fiber is inserted into the coiled wire torque spring component so that the coiled wire surrounds the fiber. Generally, stainless steel coiled wire torque spring components are comprised of three or more spring coils, with at least two of the spring coils wound in clockwise or counter clockwise direction and at least one other spring coil wound in the opposite direction. Multi-coil stainless steel construction allows these torque spring components to be rotated in either clockwise or anticlockwise direction and transmit the force without unwinding. However, torque spring components with multi-spring coils have the following draw-backs: (1) because of the complexity of these multi-coil springs and their dimensional tolerances, such torque spring components can be quite expensive; (2) because such coiled wire torque spring components are very flexible, threading them through the inner lumen is cumbersome, particularly over a length of a few meters; (3) due to the springs, there can be significant back lash, particularly during the retraction of the probe for scanning, which can lead to image resolution problems and fidelity issues; (4) spiral structure of the spring coils can lead to some stiction while the torque spring component is being threaded inside the inner lumen, which may result in non-uniform rotation and linear motion. A torque spring component made of a single stainless steel coil has similar drawbacks, but may also unwind, or experience greater backlash than the multi-coil torque tube.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.